The present invention relates to a method and apparatus of flow analysis, and, in particular, to an analyzing method and apparatus in which by introducing a liquid sample into a flow path in the apparatus, the items to be analyzed with respect to the sample flowing in the flow path are measured by a measuring electrode.
In, for example, U.S. Pat. No. 4,452,682, a flow analysis arrangement is provided wherein a plurality of measuring electrodes are arranged along a flow path in which a sample is flowing, and items to be analyzed including gas components, electrolyte, urea, nitrogen, etc., contained in blood are sequentially measured. A pump for transferring the blood sample through the flow path is disposed downstream of the measuring electrodes. As a result, when the flow path is blocked at the entry port for the sample, or a phenomenon of blockage occurs, the pressure within the flow path is reduced. The abnormal pressure drop in the flow path adversely affects the measuring electrodes. In particular, when an oxygen measuring electrode is of the Clark type and when a carbon dioxide measuring electrode is of the Severinghaus type, measured values are affected to a great extent due to the pressure drop.
For example, the carbon dioxide measuring electrode includes an inner electrode, an inner electrolyte solution, and a gas permeable membrane. When this measuring electrode is disposed in the flow path in which the sample is flowing, only the gas permeable membrane is interposed between the flow path and the inner electrolyte solution. Accordingly, the tension of the gas permeable membrane is varied due to a change in pressure within the flow path, and consequently, the accuracy in measurement is degraded.